DC electric motors take many forms, depending upon application, required performance and cost considerations. The permanent magnet brush/commutator DC motor is widely used. The brushless permanent magnetic motor is becoming popular, mainly because it offers enhanced, consistent performance, lacking the brushes that wear out over time and produce RFI. On the other hand, a brushless motor uses electronic (solid state) controls to synthesize the commutation effect, adding cost and complexity to some degree. The operation of brushless motors is well known. Hall effect devices or other detectors are used to sense field orientation as the rotor rotates. Semiconductor switches (e.g. junction transistors) may be used to switch/regulate the "high side" and "low side" field currents in the motor.
DC motors are proliferating in the typical automobile as automobiles increasingly include more powered features. These motors are used for windshield wipers, for each electrically operated window, for door locks, for hood and trunk locks, for sunroof operators, for blowers, and for active suspensions, just to name a few applications. They are also used for radiator and air conditioning condenser fans. Each application calls for a motor with a specific operating characteristic and a tailored drive, the system by which power is applied from the vehicle supply to the motor. Some motors may have multiple speeds; some may operate at constant speed; some may have to reverse; some may be brush type or brushless; and some may use dynamic braking in different forms to rapidly slow the motor.
The interface between the motor and the operator therefore can add considerably to vehicle cost if each motor must have its own motor controller. Traditionally, each motor has had a customized controller or interface. Considering the number of possible motors that can be present in a vehicle, such as an automobile, this increases the cost substantially. Adding to the cost, power to each motor is routed through power from the supply through a switch.